The 'new' Kanchanaburi township was constructed in 1831 at the confluence of the Kwae Noi and Kwae Yai rivers during the reign of Rama III as both a trade route and effective defensive post against potential attacks from the Burmese. As part of this, a wall was built to protect the town however all that remains now is this one section along with the gate.
Kanchanaburi is now a bustling tourist town in a beautiful part of Thailand and is the gateway to exploring the rich, but sad, WWII history in the area. It's well worth spending a few days here to soak up the atmosphere and scenery! :)